How do you start making cosmetics?

I had a couple questions about cosmetics. First, when you do make a cosmetic-what process does it go through before it gets implemented into the game? Like does it have to go through the Steam Workshop before they add it?

Also, most important of all. How do you go about making an item? I know you need skills in 3-D Modeling and maybe animation to create an item but what programs would you use? Something like Photoshop or Maya? And also, for the rarer item sets, I notice the particle effects and custom icons-how would you go about making those?

There were a lot of questions there-I'm just interested in that sort of stuff so any answers would be greatly appreciated thanks!

This should help you

http://www.dota2.com/workshop/